Sex abuse victim Derek Mulligan today demanded to know why his abuser Michael Ferry was allowed to continue to work as a school caretaker after an earlier conviction.

He asked why Ferry was able to return to his job at Ard Scoil Mhuire in Gweedore in 2002.

"Why did his employers still employ him? There's so many questions," he told RTE's Moring Ireland in an emotional plea.

He added he will keep asking the question until he gets answers.

Derek Mulligan (24), from Gweedore, Co Donegal, bravely waived his anonymity to urge other victims of sexual abuse to come forward and report it to gardai in order to "end your nightmare".

"How can someone so sick prey, not even on people his own age but children -- the most vulnerable of all -- just for his own kicks and pleasures?" he asked after Ferry was jailed for 14 years yesterday.

Mr Mulligan was one of four boys who were systematically groomed and abused by the local school caretaker.

Given Ferry's previous conviction for sexual assault almost nine years ago -- and that he continued to abuse again and again -- his expression of remorse was meaningless to Mr Mulligan.

"Did he say the same to that victim that day in 2002, that he had remorse for what he had done to them? But yet he still goes on to abuse again. Does he even know what remorse means?" Mr Mulligan asked. "I believe someone so sick and perverted could never change."

Mr Mulligan described how years of abuse had destroyed his childhood.

"Basically what happens is it ruins your life. First you lose your childhood; then, the more you try to bury it, it eats away at you, bit by bit. It even haunts your dreams."

However, he believes there is light at the end of such a dark tunnel and the first step toward him regaining his life was reporting the abuse to gardai.

"It wasn't until I came forward that my nightmare ended. My advice to anyone is 'don't hold it inside any longer. Talk to the gardai, end your own nightmare'."